Controls for refrigeration systems having air cooled condensers



Nov. 26, 1963 ROBERTS 3,111,815

' D. B. CONTROLS FOR REFRIGERATION SYSTEMS HAVING AIR COOLED CONDENSERSFiled April 20, 1962 2 Sheets-Sheet 1- EVAPORATOR EXPANSION AIR COOLE'Da8 3a a7 f 2 .4 I l3 --&6 CHECK VALVE 1g 1 TURBINE a5 HE J H v PUMP 1 JCOM T Eg S OR CONTROL 5 1 VALVE 33 PRESSURE RELIEF VALVE 1 :29-62,

liwezai'ozt- Deweg;B.Robe2wq ymmzavw Nov. 26, 1963 B. ROBERTS 3,111,815

D. CONTROLS FOR REFRIGERATION SYSTEMS HAVING I AIR COOLED CONDENSERSFiled April 20, 1962 2 Sheets-Sheet 2 a/ EVAPORATOR 5 as s so EXPANSIONe'c'iNs s R 3a a e7 /a l m ,67 i CHECK VALVE a 3 HERMETIC COMPRESSOR cNTROL VALVE RELIEF VALVE 122 .4.

United States Patent 3,111,315 CGNTROLS FOR REFRTGERATEON SYSTEMS HAVINGAER CQQLED (JONDENSERS Dewey B. Roberts, Decatur, Ga, assignor toWestinghouse Eiectric Corporation, East Pittsburgh, Pa, a corporation ofPennsylvania Filed Apr. 24), 1962, Ser. No. 189,056 3 Claims. (CL622tl9) This invention relates to controls for refrigeration and airconditioning systems using air cooled condensers.

Due to the lack of sufficient water in many locations to water cool thecondensers of refrigeration and air conditioning systems, and due to thecost of water cooling such condensers in those locations wheresufiicient water is available, air cooled condensers are widely used. Inmany air conditioning systems for buildings where delicate equipmentsuch as computers is used, their refrigeration systems are operatedduring cold as well as hot weather. When the condenser of such a systemis cooled by outdoor air as is usual, low outdoor temperature may causesuch low condensing pressures that there is insuflicient refrigerantpressure to properly operate an expansion valve or other expansionmeans. This problem is well known, and many expedients have beenproposed for solving it. Among such expedients have been the starting ofa condenser fan, and opening and closing condenser dampers by controlsresponsive to refrigerant pressure, and the flooding of a condenser toreduce its effective condensing surface for causing an increase inpressure. Such expedients have been inefficient, and have not beensatisfactory.

This invention provides adequate pressure'at an expansion device byboosting the liquid pressure when the pressure difference across theexpansion device decreases to the point that it is ineffective. In oneembodiment of this invention, a gas turbine driven by discharge gas froma refrigerant compressor, drives a liquid pump which boosts the liquidpressure. The turbine is controlled by a valve which responds to thepressure difference between the liquid and suction lines. When thepressure difference exceeds a predetermined minimum, which may be 120p.s.i., the control valve permits all of the discharge gas to by-passthe turbine. A liquid by-pass around the pump includes a check valvewhich is open at this time permitting the liquid to by-pass the pump.When the pressure difference decreases to the predetermined minimum, thecombination of suction pressure and spring pressure within the controlvalve overcomes the liquid pressure within the control valve, andpositions a slidable piston within the control valve so as to providesufficient discharge gas pressure drop across the turbine. The turbinethen is in operation, driving the liquid pump to boost the liquidpressure to the desired level, thereby causing the pressures at each endof the control valve to always stay in balance. Any change in dischargeor suction pressure will automaticallycause the valve piston toreposition for a greater or lesser pressure drop across the turbine. Thecontrol valve piston will also change its position as the expansiondevice opens and closes, thereby always maintaining a constant pressuredifference between the liquid and suction lines.

An object of this invention is to maintain a constant pressuredifference between the liquid and suction lines of a refrigerationsystem.

Another object of this invention is to boost liquid pressure within arefrigeration system with a pump driven through a gas turbine bydischarge gas, and to control the operation of the turbine so as tomaintain a constant pressure between the liquid and suction lines of thesystem.

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This invention will now be described with reference to the annexeddrawings, of which:

FIG. 1 is a diagrammatic view of a refrigeration system embodying thisinvention;

FIG. 2 is a cross-section of the turbine control valve of FIG. 1;

FIG. 3 is a diagrammatic view of another refrigeration system embodyingthis invention, and

FIG. 4 is a cross-section of the turbine control valve of FIG. 3.

Referring first to FIGS. 1 and 2, a hermetic compressor 10 is connectedby discharge tube 11 to inlet port 12 of control valve 13. The valve 13has one outlet port 14 connected to the inlet of gas turbine 16, theoutlet of which is connected by tube 17 to the inlet of air-cooledcondenser 18. The valve 13 has another outlet port 20 connected by gasby-pass tube 21 to the tube 17. The turbine 16 drives a liquid pump 22,the inlet of which is connected by tube 23 to the outlet of thecondenser 18. Tubing 19 containing a pressure relief valve 37 isconnected across the pump 22. The outlet of the pump 22 is connected bytube 26 to expansion valve 27 which is connected by tube 28 to the inletof the evaporator 29. A pump by-pass tube 24 containing a check valveconnects the tube 23 to the tube 26. The outlet of the evaporator 29 isconnected by suction tube 3% to the suction side of the compressor 10.The expansion valve 27 is a conventional one controlled by a thermostat31 responsive to the temperature of the evaporator. The top of thecontrol valve 13 is connected by a tube 32 to the tube 3% and its bottomis connected by a tube 33 to the tube 26.

As shown by FIG. 2, the control valve 13 is cylindrical with its inletport 12 in one side and its outlet ports 14 and 2t spaced apart in itsopposite side. The valve 13 contains a slidable piston 35 in which thereis a passage 36 for connecting the inlet port 12 with either or both ofthe outlet ports 14 and 20, with a rib 34 midway between the outlet endof the passage 36. When the piston is in its lowermost position, itssolid upper portion blocks the port 29, and the lower edge of the rib 34lines up with the top of the port 14. When the piston is in itsuppermost position, its solid lower portion blocks the port 14, and theupper edge of the rib 34 lines up with the bottom of the port 20. Thetop of the piston 35 is recessed to receive the lower portion of acoiled spring 38, the lower end of which touches the piston at thebottom of its recess, and the upper end of which is in contact with thebottom of a disc 48, the top of which is in contact with the lower endof a screw 4% threaded into top wall 39 of the cylinder, and extendingthrough a packing nut 41 threaded in a sleeve 42 formed on the top ofthe wall 39. The screw is adjustable from exterior of the valve 13 tovary the compression of the spring 38.

A fitting 44 screwed into the top wall 39 of the valve 13 connects asuction pressure chamber between the top of the piston 35 and the wall39, with the suction gas tube 32. A fitting 46 screwed into bottom wall47 of the valve 13, connects a liquid pressure chamber between thebottom of the piston 35 and the bottom wall 47, with the liquid tube 33.

in the normal operation of FIGS. 1 and 2, when the outdoor temperatureis not low enough to lower the condensing pressure to the point Wherethe expansion valve 27 is ineffective, the check valve 25 will be openand the liquid pressure supplied through the tubes 24, 26 and 33 to thebottom of the piston 35 of the valve 13 will be greater than that of thesuction gas pressure and the pressure of the spring 38 at the top of thepiston, so that the piston will move up to close the outlet port 14connected to the turbine 16, and to open the outlet port 2% corn nectedto the turbine by-pass tube 21. The turbine 16 3 and the pump 22 do not,therefore, operate. Liquid iiows from the bottom of the condenser 18through the pump lay-pass tube 24, check valve 25 and the tube 2.6 tothe expansion valve 27.

'When the outdoor temperature decreases to a point where the condensingpressure is too low for the expansion valve 27 to operate properly, thesuction pressure and the pressure of the spring 38 on top or". thepiston will be greater than the liquid pressure on the bottom of thepisten 35, so that the latter will move down to cover the outlet port 26connected to the turbine by-pass tube 21, and to open the outlet port 14connected to the turbine 26. The turbine is operates the pump 22 toboost the liquid pressure, the liquid flow being from the bottom of thecondenser 18, through the tube 23, the pump 22 and the tube 26 to theexpansion valve. The pump 22 at this time exerts a higher pressure inthe tube 24 than in the tube 23, causing the check valve 25 to close.The relief valve 37 functions as a safety device to by-pass liquid fromthe tube 26 through the tube ii) to the tube 23 in the event or" amalfunction of the turbine control valve 13. The check valve 23 could bebuilt into the pump 22.

The pressures at each end of the control valve piston are equal sinceany unbalance due to any change in discharge pressure or suctionpressure will automatically reposition the piston for a greater or lesspressure drop across the turbine 16. The piston of the control valvewill also vary its position as the expansion valve moves towards open orclosed position, thereby always maintaining a desired constant pressuredifference between the liquid and suction lines.

Adjustment of the spring pressure varying screw lt? permits the controlvalve to be adjusted to maintain dilferent desired pressure drops acrossthe expansion valves. The spring 38 can be changed for one havingdilferent characteristics as may be required where the evaporator islocated at different levels.

The embodiment of the invention shown by FIGS. 3 and 4 is generallysimilar to that shown by FIGS. 1 and 2 and differs therefrom only byhaving a different control valve construction, and having differentconnections to the control valve. The components of FIG. 3 which aresimilar to corresponding ones of FIG. 1 are given the same referencecharacters.

Control valve 5t) of FIGS. 3 and 4, has an inlet port 51 connected tothe discharge pipe 11, and has a single outlet port 52 aligned with theport 51, and connected to turbine by-pass tube 53. The valve 5% has apiston 55 with a passage 56 extending therethrough. The piston 55 has arecess in its head with a spring 57 therein similar to the recess andspring 38 respectively, of FIG. 2; has a disc 58 on top of the spring57, and an adjusting screw 59 threaded in sleeve 60 on top wall 61 ofthe valve 50 and extending through a packing nut 62. A fitting 64connects the suction gas chamber between the top of the piston 5 and thevalve top wall 61 with suction gas tube 32. Fitting 67 threaded intobottom wall 68 of the valve 54) connects the liquid chamber between thebottom of the piston 55 and the valve bottom wall ed to the liquid tube33.

The valve 58 has an adjustable screw '70 threaded into sleeve 71 on thebottom of the valve bottom wall 68, and extending through a packing nut74, the inner end of which acts as an adjustable stop for the bottom ofthe piston 55 for preventing possible damage to the turbine on start upas might occur if all of the discharge gas was supplied to the turbine.The screw 76 prevents the outlet port 52 connected to the turbineby-pass from being fully closed by down movement of the piston 55.

The inlet of the turbine 16 instead of being connected to an outlet portin the control valve 54 is connected directly to the discharge gas tube11 by a discharge gas tube 75.

The embodiment of FiGS. 3 and 4 operates similar to that of FIGS. 1 and2, the only difference being that the central valve Etl only opens abypass around the turbine when its piston 55 is moved upwardly, and doesnot at the same time close oil the supply of discharge gas to theturbine as in the operation of FIGS. 1 and 2. The resistance to howthrough the turbine is sufiicient to cause all of the discharge gas toflow through the by-pass tube 53 of FIG. 3 when the valve piston 55 ofthe valve 50 opens its outlet port 52.

What is claimed is:

1. In a refrigeration system having a compressor, an air cooledcondenser, an expansion device, and an evaporator connected in series inthe order named in a refrigeration circuit, the combination of a liquidpump connected in said circuit between said condenser and said devicefor pumping liquid from said condenser to said device, means including acheck valve forming a by-pass around said pump for flowing liquid fromsaid condenser to said device when said pump is not operating, a gasturbine connected in said circuit between said compressor and saidcondenser and connected to said pump to drive said pump, means forming asecond by-pass around said turbine, and means included in said secondby-pass and including means responsive when said check valve is closed,to the difference between the suction pressure at said compressor andthe liquid pressure at said expansion device for increasing the flow ofgas through said second by-pass when said difference exceeds apredetermined minimum and for decreasing the flow of gas through saidsecond by-pass when said difference is at or is less than said minimum.

2. In a refrigeration system having a compressor, an air cooledcondenser, an expansion device, and an evaporator connector in series inthe order named in a refrigeration circuit, the combination of a liquidpump connected in said circuit between said condenser and said devicefor pumping liquid from said condenser to said device, means including acheck valve forming a by-pass around said pump for flowing liquid fromsaid condenser to said device when said pump is not operating, a gasturbine connected in said circuit between said compressor and saidcondenser and connected to said pump to drive said pump, means forming asecond by-pass around said turbine, means included in said secondby-pass and including means responsive to the difference between thesuction pressure at said compressor and the liquid pressure at saidexpansion device for increasing the flow of gas through said secondby-pass when said diiference exceeds a predetermined minimum and fordecreasing the flow of gas through said second by-pass when saiddifference is at or is less than said minimum, and means including apressure relief valve connected around said pump.

3. In a refrigeration system having a compressor, an an cooledcondenser, an expansion device, and an evaporator connected in series inthe order named in a refrigeration circuit, the combination of a liquidpump connected in said circuit between said condenser and said devicefor pumping liquid from said condenser to said device, means including acheck valve forming a by-pass around said pump for flowing liquid fromsaid condenser to said device when said pump is not operating, a gasturbine connected in said circuit between said compressor and saidcondenser and connected to said pump to drive said pump, means forming asecond by-pass around said turbine, and means included in said secondby-pass and included in the connection of said turbine to saidcompressor and including means responsive to the difference between thesuction pressure at said compressor and the liquid pressure at saidexpansion device for increasing the flow of gas through said secondby-pass and decreasing the flow of gas through said turbine andincreasing the fiow of gas through said turbine when said differenceexceeds a predetermined minimum, and for decreasing the flow throughsaid second by-pass and increasing the flow earners of gas through saidturbine when said difference is at or is less than said minimum.

4. In a refrigeration system having a compressor, an air-cooledcondenser, an expansion device, and an evaporator connected in series inthe order named in a refrigerw tion circuit, the combination of a liquidpump connected in said circuit between said condenser and said devicefor pumping liquid from said condenser to said device, means including acheck valve forming a bypass around said pump for flowing liquid fromsaid condenser to said device when said pump is not operating, a gasturbine connected in said circuit between said compressor and saidcondenser and connected to said pump to drive said puml means forming asecond by-pass around said turbine, means included in said secondby-pass and included in the connection of said turbine to saidcompressor and includin means responsive to the difference between thesuction pressure at said compressor and the liquid pressure at saidexpansion device for increasing the flow of gas through said turbinewhen said difference exceeds a predetermined minimum, and for decreasingthe flow of gas through said second by-pass and increasing the flow ofgas through said turbine when said ditlerence is at or is less than saidminimum, and means including a pressure relief valve connected aroundsaid pump.

5. In a refrigeration system having a compressor, an air cooledcondenser, an expansion device, an evaporator, and tubing connecting theoutlet of said device to the inlet of said evaporator and the outlet ofsaid evaporator to the suction side of said compressor, the combinationof a liquid pump having its inlet connected to the outlet of saidcondenser and having its outlet connected to the inlet of said device,means including a check valve forming a bypass around said pump forsupplying liquid from said eondenser to said device when said pump isnot operating, a control valve having an inlet connected to thedischarge side of said compressor, and having an outlet, a gas turbineconnected to said discharge side of said compressor and having itsoutlet connected to the inlet of said condenser, by-pass tubingconnected to said outlet of said control valve and to said inlet of saidcondenser, said turbine being connected to said pump to drive said pump,a piston slidable in said control valve and having a passage for passinggas from said valve inlet to said valve outlet, means including a tubeconnecting said suction side of said compressor to the interior of saidcontrol valve at one end of said piston, and means including a tubeconnecting said inlet of said device to the interior of said controlvalve at the opposite end of said piston.

6. In a refrigeration system having a compressor, an air-cooledcondenser, an expansion device, an evaporator, and tubing connecting theoutlet of said device to the inlet of said evaporator and the outlet ofsaid evaporator to the suction side of said compressor, the combinationof a liquid pump having its inlet connected to the outlet of saidcondenser and having its outlet connected to the inlet of said device,means including a check valve forming a bypass around said pump forsupplying liquid from said condenser to said device when said pump isnot operating, a control valve having an inlet connected to thedischarge side of said compressor, and having an outlet, a gas turbineconnected to said discharge side of said compressor and having itsoutlet connected to the inlet of said condenser, by-pass tubingconnected to said outlet of said control valve and to said inlet of saidcondenser, said turbine being connected to said pump to drive said pump,a piston slidable in said control valve and having a passage for passinggas from said control valve inlet to said control valve outlet, meansincluding a tube connecting said suction side of said compressor to theinterior of said control valve at one end of said piston, meansincluding a tube connecting said inlet of said device to the interior ofsaid control valve at the opposite end of said piston, and meansincluding a pressure relief valve connected around said pump.

7. in a refrigeration system having a compressor, an air cooledcondenser, an expansion device, an evaporator, and tubing connecting theoutlet of said device to the inlet of said evaporator, and the outlet ofsaid evaporator to the suction side of said compressor, the combinationof a liquid pump having its inlet connected to the outlet of saidcondenser, and having its outlet connected to the inlet of said device,means including a check valve forming a bypass around said pump forflowing liquid from said condenser to said device When said pump is notoperating, a control valve having an inlet connected to the dischargeside of said compressor and having spacedapart, first and secondoutlets, a gas turbine having its inlet connected to said first outletand having its outlet connected to the inlet of said condenser, a secondby-pass tube connected to said second outlet and to said inlet of saidcondenser, a piston slidabie in said control valve and having a passagefor connecting said valve inlet with either or with portions of both ofsaid first and second outlets, means including a tube connecting saidsuction side of said compressor into the interior of said control valveat one end of said piston, and means including a tube connecting saidinlet of said device to the interior or" said control valve at theopposite end or" said piston.

8. in a refrigeration system having a compressor, an air cooledcondenser, an expansion device, an evaporator, and tubing connecting theoutlet of said device to the inlet of said evaporator, and the outlet ofsaid evaporator to the suction side of said compressor, the combinationof a liquid pump having its inlet connected to the outlet of saidcondenser, and having its outlet connected to the inlet of said device,means including a check valve forming a lay-pass around said pump forflowing liquid from said condenser to said device when said pump is notoperating, a control valve having an inlet connected to the dischargeside of said compressor and having spaced-apart, first and secondoutlets, a gas turbine having its inlet connected to said first outletand having its outlet connected to the inlet of said condenser, a secondby-pass tube connected to said second outlet and to said inlet of saidcondenser, a piston slidable in said control valve and having a passagefor connecting said valve inlet with either or with portions of both or"said first and second outlet-s, means including a tube connecting saidsuction side of said compressor into the interior of said control valveat one end of said piston, means including a tube connecting said inletof said device to the interior of said control valve at the opposite endof said piston, and means including a pressure relief valve connectedaround said pump.

References Cited in the file of this patent UNITED STATES PATENTS2,156,096 Robinson Apr. 25, 1939 2,394,169 Sanchez Feb. 5, 19462,949,750 Kramer Aug. 23, 1960 3,081,606 Brose et al. Mar. 19, 1963

1. IN A REFRIGERATION SYSTEM HAVING A COMPRESSOR, AN AIR COOLEDCONDENSER, AN EXPANSION DEVICE, AND AN EVAPORATOR CONNECTED IN SERIES INTHE ORDER NAMED IN A REFRIGERATION CIRCUIT, THE COMBINATION OF A LIQUIDPUMP CONNECTED IN SAID CIRCUIT BETWEEN SAID CONDENSER AND SAID DEVICEFOR PUMPING LIQUID FROM SAID CONDENSER TO SAID DEVICE, MEANS INCLUDING ACHECK VALVE FORMING A BY-PASS AROUND SAID PUMP FOR FLOWING LIQUID FROMSAID CONDENSER TO SAID DEVICE WHEN SAID PUMP IS NOT OPERATING, A GASTURBINE CONNECTED IN SAID CIRCUIT BETWEEN SAID COMPRESSOR AND SAIDCONDENSER AND CONNECTED TO SAID PUMP TO DRIVE SAID PUMP, MEANS FORMING ASECOND BY-PASS AROUND SAID TURBINE, AND MEANS INCLUDED IN SAID SECONDBY-PASS AND INCLUDING MEANS RESPONSIVE WHEN SAID CHECK VALVE IS CLOSED,TO THE DIFFERENCE BETWEEN THE SUCTION PRESSURE AT SAID COMPRESSOR ANDTHE LIQUID PRESSURE AT SAID EXPANSION DEVICE FOR INCREASING THE FLOW OFGAS THROUGH SAID SECOND BY-PASS WHEN SAID DIFFERENCE EXCEEDS APREDETERMINED MINIMUM AND FOR DECREASING THE FLOW OF GAS THROUGH SAIDSECOND BY-PASS WHEN SAID DIFFERENCE IS AT OR IS LESS THAN SAID MINIMUM.